1. Field of the Invention
The invention relates to an image transfer sheet for transferring an image developed thereon to an image receiving surface such as a post card, ordinary paper, a plastic sheet or a cloth.
2. Description of Related Art
It is known to record an image using a combination of photo-sensitive and pressure-sensitive recording medium which includes a base sheet and, supported thereon, a layer of microcapsules each filled with an inside phase containing a photo-curable substance, a photo-initiator and a dye precursor as main ingredients thereof, and a developer sheet which includes a substrate and a developer layer supported thereon. The developer colors by the reaction with the dye precursor.
Recording medium capable of recording an image by hardening of microcapsules is well known. Also known is a recording medium in which microcapsules and a developer are supported on a common substrate. See for example, U.S. Pat. Nos. 4,501,809, 4,399,209 and 4,440,846.
In such a recording medium, the record of an image is effected by utilizing the phenomenon that the micro-capsules are changed into rigid particles by the hardening of the internal photo-curable substance by irradiation with light.
Such a recording medium may be used in an recording system in which the recording medium is subjected to image-wise exposure, followed by rupture of non-exposed microcapsules to form a copy image by reaction of the encapsulated dye precursor with the developer.
With the above-mentioned photo-sensitive and pressure-sensitive recording medium, an image can be formed only on the specifically processed recording medium per se or the developer sheet; i.e., it is impossible to form images on an ordinary paper such as a post card, a plastic film, a cloth or other desired surfaces.
A system in which an image transfer, developer sheet having a base sheet provided thereon with an intermediate, thermoplastic resin layer and a top, developer layer is used for forming an image on an image forming surface such as ordinary paper is disclosed in U.S. Pat. No. 5,019,475.
With this system, the image transfer, developer sheet is placed with its developer layer in face to face contact with an image-exposed microcapsule layer of a photo-sensitive and pressure-sensitive recording medium to form an image on the developer sheet. Thereafter, the image-carrying developer sheet is brought into contact with an image receiving surface such as ordinary paper with heating. By peeling away the base sheet, a transferred image is formed on the image receiving surface.
The known image transfer, developer sheet, however, has been found to involve the problem that a clear image is not always obtainable on the image receiving surface because the developer layer tends to be torn or peeled off from the thermoplastic resin layer during use. Thus, when the transfer sheet is warped such as during transference of the developed image from the transfer sheet to an image-receiving surface, the transfer layer occasionally splits or falls off.
Further, the transfer layer is apt to be peeled off from the thermoplastic resin layer during the severing of a master roll thereof with a cutter or during handling.
It has now been found that the above problem is attributed to poor affinity or compatibility between the developer layer and the thermoplastic resin layer and to poor flexibility of the developer layer. Therefore, the developer layer tends to be cracked or to split upon receipt of an external force.